Process of recovering sodium tetraborate from borate ores



Patented Dec-f 26, 1939 PROCESS OF RECOVERJNG SODIUM TET- RABORA'I'E FROM BORATE OR-ES Plato Malozemofi and Merrill w. MacAfee, Oakland, and Miles W. Kirk, Berkeley, Calif., assignors to Pacific Coast Borax Company. acorporation of Nevada No Drawing. Application May 11;, 1931,

Serial No. 143,346

Claims. (Cl. 209-11) This invention relates to the recovery of ores V 5 sodium tetraborate from its gangue.

Flotation methods have heretofore been applied with success in the separation of minerals from each other in cases where such minerals are all insoluble in water or the separation of minerals in cases in which all the minerals are soluble in water, but the present'invention is directed to a simple and efflcient method of froth flotation as applied to an ore in which the values soluble in water are floated from the'insoluble constituents.

Further, it maybe said that with regard to the flotability of one mineral as compared with another when using fatty acid or soaps it has been considered by those skilled in the art of flotation of non-metallic minerals that the presence of an element of the heavy'metal group or of the alkaline earth group, is usually indicative of floatability of the mineral containing it. In a resented by what is known as the Baker ore, containing sodium tetraborate and certain waterinsoluble minerals that have an alkali element in their composition, it would be expected that the water-insoluble portion would float more readily than the water-solubleportion, to-wit, the sodium tetraborate. But, as carried out in the present process, it has been discovered that-the water-insoluble constituents of. .the ore do not float so readily as sodium tetraborate does, especially after suitable activation which acts selectively on the borate minerals In the Baker ore there is a large percentage-of sodium tetraborate amounting to approximately eighty (80%) percent or over, the remainder of the ore consisting largely of an insoluble gangue containing Mg, Fe, and Al silicates. v

For attaining the results desired, the process of the present invention may be carried out for example asiollows, it being understood, however, that the conditions of working may be varied within wide limits: i

'I'he first step performed, is that of grinding. This is done in any well known manner and is performed primarily for two purposes. First, to 50 reduce the .size of individual ore particles to the floatable size; and second, .to liberate the several minerals that are interlocked in the original ore so as to be able to more readily separate them.

, In the preparation of the Bakerore, it was 55 found that grinding to about fifty was necessary to reduce the ore to the floatable size and liberate the several minerals, as above noted.

In conducting the flotation of an ore such as the Baker ore the process is carried out in aqueous pulp; therefore, in continuousoperation the 5 water used to pulp the ore will soon be saturated with sodium tetraborate at the temperature that obtains during flotation. Thus, flotatio'n'is conducted'on a pulp consisting of two phases: the solid phase which is made up of the water solu- 10 ble minerals, alkali borates, and of the insoluble minerals; and the aqueous phase, which consists of saturated borate solution. The water soluble minerals remain undissolved in the saturated borate solution.

In conducting the process, the pulp of the ore with the saturated borate solution is prepared ahead of flotation by mixing the ore with the returned saturated borate solution, which is reclaimed by suitable means irom the 'tailings. 20 After the ore is ground, it is suitably diluted with saturated solution, as an example, ten parts of saturated borax solution to one part of solids by like manner, a mineral mixture, such as is Weight, and heated somewhat above he temperae that will obtain during the flotation, as'an 25 example 3 C. to 7 C. above the flotation temperature. This preheating step is desirable in order to facilitate differential flotation of the borate minerals from the insoluble gangue minerals. The pulp so preheated is forcibly cooled 30 and then floated; or else floated directly after the preheating treatment, which causes cooling to takeplace naturally inasmuch as the ore is preheated above the temperature that obtains during flotation.

. It has beeirfound that if a constant temperature be maintained before and during flotation,

, the diiferentialseparation of sodium tetraborate from the water insoluble gangue is not as marked as when the pulp is preheated previously to flo- 4o tation in which case the sodium tetraborate crystals are activated more readily and float more easily than otherwise, thus permitting a difierential. separation of the podium tetraborate from the water insoluble gangue.

Reagents that are addedprevious to and dur-r ing flotation comprise the following: an activator of the alkaline earth group, such as barium chloride, or of the'heavy metal group, such as copper sulfate; a promoter such as a fatty acid or a derivative of a fatty acid; if the promoter has frothingproperties, such reagent alone may fulflll the functions of a promoter'and frother, otherwise a separate frother, such as pine oil or cresylic acid, may used.

It will be noted from the above description of this method that the activation of the water soluble borate minerals is efiected by means of two agencies, to-wit, preheating of the pulp previous to flotation and the use of a chcemical such as one of the alkaline earth group or of the heavy metal group. Both these agencies are selective in that they enhance the flotation of water soluble borate minerals but do not show any marked tendency towards floating the insoluble gangue minerals, thus permitting a differential separation of the two constituents in the ore.

It is believed that the preheatingtreatment results in removing the surface film from the sodium tetraborate crystals which is inert (or rendered inert with time) -to the activator and promotor reagents. Also, it is believed that after the dissolution of this inert coating the efiect of partial cooling results in the formation of a fresh film of mineral on the surface of the particles, which aids in the selective action of the reagents towards the borate mineral surfaces. As an example 100 grams of Baker ore ground to all minus fifty mesh was pulped with 1000 cc. of sodium tetraborate solution saturated at 29 C. and the pulp heated to 36 C. The heated pulp was then charged into a laboratory flotation machine and agitated with external cooling on the machine until the pulp temperature again reached 29 C. Barium chloride and oleic acid were added and the sodium tetraborate minerals floated for 23.5 minutes. The rougher concentrate thus produced was suitably cleaned at constant temperature in the same machine.

The above test data is illustrative of the flotation of the borate mineral from the gangue and shows that the water insoluble content of the concentrate is 4.82% as against 15.00% in the ore and that the recovery of the borate minerals as concentrate was 73.1%.

We claim as our invention:

1. The process of treating borate ores containing sodium tetraborate and minerals non-soluble in water which consists in mixing the ore in a finely divided condition with a saturated solution of sodium tetraborate and then subjecting the pulp to a froth flotation treatment in the presence of a reagent having a preferential afiinity for the sodium tetraborate, said reagent consisting of barium chloride and a fatty acid.

2. The process of treating ores containing borates and minerals non-soluble in water, which consists in mixing the ore in a finely divided condition with a saturated solution of the borates and then subjecting the pulp to a froth flotation treatment in the presence of a reagent having a preferential aflinity for the borates, said reagent consisting of barium chloride, and a fatty acid.

3. The process of treating borate ores which consists in forming a saturated solution of borates, heating the solution above the flotation temperature, adding finely divided borate ore to the heated solution, then subjecting the pulp so formed to froth floation action in the presence of an activator reagent having an aflinity for the borates, whereby the undissolved soluble material is floated ofi the mixture.

4. The process of treating borate ores which consists in forming a saturated solution of sodium tetraborate, heating said solution to a temperaticles of the mineral, heating the pulp so formed,

partially cooling the pulp and then subjecting the pulp to froth flotation treatment.

PLATO MALOZEMOFF. NEILES W. KIRK.

MERRILL W. MACAFEE. 

